Rust inhibitor for mineral oils



Patented Dec. 13, 1949 2.4mm nus-r mmnrroa ma mean. one

Jones I. WauomUnion. and Gordon W. Duncan, 'Westfleld,N.J-,uolgnonto8tandard0ilDevelopment Company. a corporation of Delaware No Drawing. Application September 15, 1947, Serial No. 774.187

Claims. (01. us-aw This invention relates to rust inhibiting compounds and particularly to rust inhibitors of a type suitable for use like. The invention relates further to enhancing and improving the rust preventing characteristics of certain petroleum type rust preventives which have been used prior to the present invention.

In the prior art it is well known that certain soaps, that is the metallic salts of certain organic acids, have rust inhibiting properties when added to mineral oils and waxes. In particular, it is known that the metallic salts of sulfonic acids, naphthenic acids, and the like, have desirable rust inhibiting properties under certain conditions.

The materials mentioned above may be used in petroleum type protective coating compositions and under moderate conditions they prove reasonably satisfactory for inhibiting the rusting of ferrous metals. In fact, they are often effective in protecting ferrous metals from rusting in the actual presence of liquid water. It has been found, however, that under severe conditions of high humidity and relatively high temperature, these materials may fail to give adequate protection for the desired length of time. Thus, under tropical or semi-tropical conditions, airplane engines and other mechanical equipment have been found to rust rapidly when not in use despite the presence of petroleum rust preventives which are reasonably effective under average climatic conditions in more temperate zones.

It is, therefore, an object of our invention to provide improved compositions for preventing rust under severe conditions of humidity, temperature, and the like. It is a further object of our invention to modify known rust inhibitors so as to increase their effectiveness and efficiency when used in protective coating oils and slushing compositions generally.

The object stated above and other objects which we are able to accomplish by our invention will become more apparent as this description proceeds.

We have found that by the use of certain oilsoluble dipolar acids, in combination with conventional rust inhibitors of the general character described above, very effective rust protection may be provided even under the severe humidity and temperature conditions of tropical and semitropical regions. We have found in particular that protective compositions consisting largely of mineral oil products give very good protection against rust when conventional rust inhibitors in mineral oils and the R-S-CHaCOOI-I me 0 on R-S- -CHCOOH HICOOH where R represents an aliphatic hydrocarbon radical of 10 to 30 carbon atoms. preferably 12 to 22 carbon atoms or, more generally,

where R is an aliphatic radical as above, X is either sulfur or carboxyl, and R is a hydrocarbon group of not more than 4 carbon atoms.

Other ,dipolar acidic compounds which apply to this invention include organic phosphoric acids such as aliphatic di-acid phosphates. These have the formula where R represents an aliphatic group having from 10 to 30 carbon atoms, preferably 12 to 22 carbon atoms. Suitable acid phosphates are those of lauryl and of cetyl alcohols, and of mixtures of alcohols such as are produced from cocoanut oil.

To enhance oil solubility or to control corrosiveness, amines or other nitrogen bases may also be used in conjunction with the acidic products.

While a number of the above described acidic materials have been suggested as rust inhibitors for use in bulk oil systems, such as for addition to turbine oils to prevent rusting of the oil sump and other ferrous metal surfaces with which the oil may come in contact, these agents are substantially ineffective in imparting rust resistance to oily and waxy compositions designed to afford protection to metal articles by virtue of a thin film or coating of the composition. Thus, in the conventional humidity cabinet tests for 3 determining the rust protective ability of nonsiccative coatings, the addition of these materials alone to' lubricating oils even in concentrations in excess of 1% results in no detectable improvement in the rust resistance of the oil.

We have now discovered that the above described dipolar acidic materials, although ineffective in themselves, have a strong synergistic eifect on compositionscontaining the common rust inhibitors such as metallic sulfonates. It is believed that these commonly used agents owe their effectiveness primarily to their ability to bind condensing moisture vapor or other water into the protective film as a tight internal dispersion, and thus prevent access of the moisture to the coated metal surface. The mechanism for the synergistic action between the two types of materials is not entirely understood at the present time.

The following data, showing the use of substituted organic acids of the type described above in conjunction with soaps demonstrate the superiority of our improved rust inhibitors. Tests were conducted by using a standard 120 F. specification AN-H-31 humidity cabinet. This is a standard test cabinet, recognized and wisely used as such in the lubricating art and specified in U. S. Government specifications, in which uniform conditions of temperature and high humidity (95 to 100%) may be maintained. In this test, sand blasted panels of hot rolled steel are dipped into samples of the compositions to be tested, then maintained vertically in a box for 16 hours under ordinary room conditions to allow the rust preventive film to reach an equilibrium condition. Compounds containing petrolatum or waxes are applied at temperatures above their melting point and fluid products are applied at room temperatures. The coated panels are then placed in an upright position in the humidifier chamber maintained at 120 F. where they are subjected to continuous moisture condensation. The test pieces are spaced in the cabinet in such a manner that they do not come in contact with each other. The time, in hours, for a panel subjected to these conditions to develop initial evidence of rusting is observed and recorded as the resistance life of the coating composition.

The oils used in the tests were a standard transformer oil and a. standard SAE 60 grade aviation lubricating oil blended with the various rust inhibitors.

AN-H-31 humidity cabinet results Hours Life Obtained with Oil Blended with Rust Inhibitors Percent (Weight) Rust Inhibitor Indicated A ded to 011 Transformer Aviation Oil Oil 1 None 2 2 2 Alpha hexadecyl thio glycolic 2 2 3 1% Petroleum calcium sulfonaies 72 144 4 No. 3+0.03% Alpha hexadecyl thio qalyooiic acid 216 192 6 Petroleum sodium sulionates+3% neutral degras 150 150 6 No. 6 biend+0.03% Alpha hexadecyl thio glycolic acid 576+ 576+ 7 No. bIend-i-0.05% alkylated (C succinic aci 576+ 576+ 8 0.06 alkylated .(Cu) snccinic acid 2 2 The alpha hexadecyl and related thio compounds of the above table may be prepared conventionally by reacting a monochlor carboxylic acid, such monochloracetic acid and an approriate mercaptan, such as aeetyl mercaptan, with NaOH, to separate NaCl and cause a condensation to take place. Alkylated succinic and re-' lated dibasic acids are commercial products which may be obtained by alkylatlng an unsaturated dibasic acid, e. g., inaleic acid, with an appropriate long chain aliphatic compound, e. g., maleic anhydride or maleic acid is reacted with an oleiinic material such as triisobutylene which has a branched chain of 12 carbon atoms to produce a Cu alkylated succinic acid, as described in U. S. Patents Nos. 2,283,214 and 2,380,699.

The superiority of the compositions oi the present invention is clearly indicated by the above data.

In addition to the products listed above, various auxiliary agents which are suitable for use in slushing compounds and rust preventing oils generally may be employed. Examples of these are the metal salts of naphthenic acids, amine' salts of organic acids, and the like.

A suitable composition of the character referred to above may consist-of a refined or unrefined mineral oil, wax, asphalt or mixture thereof compounded with about 1 to 10% by weight, based on the total composition of a convenional rust inhibitor, such as calcium petroleum sulfonate, barium petroleum sulionate, and the like, and 0.01 to 2% by weight of a substituted acid, such as one of the acids described in detail herein above. Various other materials may be added, such as degras, 1 to 10% by weight, as is well known in the art.

The petroleum base for the protective coating composition consists of lubricating oil, wax,

petrolatum, or asphalt separately or in combina-' tion, depending upon the application intended, and may be thinned with a volatile petroleum fraction for ease of handling. Various metal sulfonates may be used, such as those derived from petroleum by drastic treatment with strong sulfuric acid, followed by neutralization with a metallic base, and these may be mixed in various proportions. Thus, a typical formula may consist of mineral oil blended with 3% of sodium petroleum sulfonate, 0.5% calcium petroleum sulfonate and 0.03% of alpha hexadecyl thio glycolic acid. More broadly, a satisfactory composition may consist of about 97 to 99% petroleum vehicle by weight, 1 to 3% of an oil soluble metal sulfonate, and about 0.01 to 1%. preferably about 0.03%, of Cm alkylated succinic acid or C1: to Ca: alkylated thio acid, the acid ingredient having two polar groups, one of which is COOH and the other of which is COOH or a thio group; the two polar groups being separated by 1 to 4 carbon atoms.

Another suitable formula consists of mineral oil blended with 3% sodium naphthenate, 3% degras, and 0.03% of alkylated (Cm) succinic acid. The sodium naphthenate may be replaced wholly or in part by sodium or calcium petroleum sulfonates.

Other formulae having the same general characteristics comprise non-volatile petroleum fractions blended with 2 to 7% of alkali or alkaline earth metal petroleum sulfonate, particularly an oil soluble sulfonate, 0 to 5% of degras, and generally 0.01 to 1.0% of C10 to C30, preferably Cu to C22 alkyl thio acid, preferably alpha hexadecyl or octadecenyl malonio acid, or alpha octadecyl thio glycolic acid or the related derivatives of propionic acid or succinic acid.

The ingredients, other than the petroleum base may be compounded as an additive in concentrated form, if desired, to be added subsequently to a suitable vehicle. Thus 1 to parts of the rust inhibitor may be blended with 0.01 to 2 parts, preferably 0.01 to 1 part of the acidic material. The vehicle may contain fatty oils of animal or vegetable origin, if desired.

We claim:

1. A rust inhibiting composition consisting essentially of a non-volatile petroleum base, a rust inhibiting proportion of an oil soluble petroleum metal sulfonate, and 0.01 to 2% of an oil-soluble alkylated acidic material having two polar groups of which one is COOH and the other is selected from the class consisting of COOH and sulfur. the polar groups being separated by at least one and not more than 4 carbon atoms and-the alkylating group having between 10 and 30 carbon atoms.

2. A coating composition consisting essentially of at least 88% by weight of a petroleum fraction, a conventional rust inhibitor taken from the class of oil soluble petroleum sulfonates, and an activator for said rust inhibitor, said activator consisting of a compound having the general formula RXR'COOH where R is an aliphatic radical having from 10 to 30 carbon atoms, x is selected from the group consisting of thio and carboxyl radicals, and R is an alkyl radical having at least one and not more than 4 carbon atoms.

3. A coating composition consisting of at least 88% by weight of a petroleum vehicle, a quantity of oil soluble petroleum sulfonate rust inhibitor suflicient to inhibit rusting of ferrous metals under average normal atmospheric conditions, and an activator for said inhibitor, said activator being an oil-soluble C10 to C30 alkylated acidic material having two separate polar groups of which one is a terminal carboxyl group said carboxyl group being separated by at least one and not more than 4 carbon atoms from a second polar group selected from the class which consists of thio and carbonyl radicals.

4. A composition as in claim 3 wherein said activator is hexadecyl thio glycolic acid.

5. A rust inhibiting composition consisting essentially of a petroleum vehicle containing from 1 to 10% by weight of a metal-salts! petroleum sulfonic acid as a rust inhibitor and 0.01 to 2% of an oil soluble alkylated acidic material having two separate polar groups separated by at least one and not more than 4 carbon atoms, of which one polar group is carboxyl and the other is selected from the class consisting of carboxyl and sulfur, said acidic material also having an aliphatic radical of 10 to 80 carbon atoms.

6. A composition according to claim 5 wherein said acidic material is hexadecyl thio glycolic acid.

'7. A composition according to claim 5 wherein said acidic material is octadecyl succinic acid.

8. A composition for imparting rust inhibiting properties to a petroleum base vehicle, comprising 2 to '7 parts'by weight of an oil-soluble metal petroleum sul'onate, 0 to 5 parts of degras, and 001 to 1 part of a Cu to C22 alkyl thio acid in which the thio and acid groups are separated by at least one and not more than 4 carbon atoms.

9; A rust inhibiting coating composition consisting essentially of about 97 to 99% by weight of a petroleum vehicle, 1 to 3% of an oil-soluble metal petroleum sulfonate. and about 0.01 to 0.1% of an alkylated thio acid having an alkyl radical of 12 to 22 carbon atoms in which the thio and acid groups are separated by at least one and not more than 4 carbon atoms.

10. A composition consisting essentially of about 94% by weight of mineral oil, 3% sodium petroleum sulfonate, 3% degras, and 0.03% alpha hexadecyl thio glycolic acid.

JONES I. WASSON. GORDON W. DUNCAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES ra'ran'rs Number Name Date 2,080,299 Banning et al. May 11, 1937 2,182,902 Lebo Dec. 12, 1939 2,184,052 zimmer et al. Dec. 26, 1939 2,349,044 Jahn May 16, 1944 2,383,792 Jahn Nov. 28, 1944 2,383,083 Adams et al. Aug. 21, 1945' 1039M. Oct. 26 

